How to implement The NOT IN clause in LINQ?

First way:

var query =

from c in dc.Customers

where dc.Orders.FirstOrDefault(o=>o.CustomerID == c.CustomerID) ==  null

select c;

Second way:

var query =

from c in dc.Customers

where !(from o in dc.Orders

select o.CustomerID)

.Contains(c.CustomerID)

select c;

http://introducinglinq.com/blogs/marcorusso/archive/2008/01/14/the-not-in-clause-in-linq-to-sql.aspx

How to hide a column in Gridview?

If set visible to false in Gridview template, this column will not be rendered into html.  

<asp:BoundField DataField="ID" HeaderStyle-Width="0px" Visible="false" />

 Should add onrowdatabound event handler to do that:

<asp:GridView ID="GridView1" runat="server" onrowdatabound="GridView1_RowDataBound">

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)

{

    if (e.Row.RowType != DataControlRowType.DataRow) return;

    e.Row.Cells[1].Visible = false;

}

ModelBinder Conventions in ASP.NET MVC

http://areaofinterest.wordpress.com/2011/03/07/announcing-asp-net-mvc-modelbinder-conventions/